A charge trap nonvolatile semiconductor memory using a charge trap charge storage insulating film as a charge storage layer has been proposed. In the charge trap nonvolatile semiconductor memory, a charge injected to a charge storage insulating film through a tunnel insulating film is trapped in a trap level of the charge storage insulating film. In this way, a charge is stored in the charge storage insulating film. A block insulting film for blocking a charge is provided between a charge storage insulating film and a control gat electrode. A MONOS or SONOS nonvolatile semiconductor memory has been known as a typical example of the charge trap nonvolatile semiconductor memory.
However, the foregoing charge trap nonvolatile semiconductor memory has the following problem on the reliability. Specifically, if a charge storage insulating film is continuously formed between neighboring memory cells, a charge stored in the charge storage insulating film leaks. Moreover, if a tunnel insulating film or block insulating film is continuously formed between neighboring memory cells, there is a possibility that a problem on the reliability arises.
In order to solve the foregoing problem, the foregoing charge storage insulating film, tunnel insulating film or block insulating film is not continuously formed between neighboring memory cells. This is effective. However, according to the conventional case, a method of effectively forming a charge storage insulating film, tunnel insulating film or block insulating film has not been proposed. Therefore, it is difficult to form a semiconductor device, which is excellent in reliability.